John,
I have not been in Goldenwing/Bluewing breeding territory that much and have
not encountered this. But I do know that it has been encountered in the
past, and is not considered extremely unusual. A few early papers (1960's)
on these species noted individuals of pure or nearly pure appearance singing
the other species song at their contact zone at a couple of locations in New
York, where the Bluewing had expanded its range and come into contact with
the Goldenwing. Also noted have been occasional "bilingual" individuals that
can sing both songs. One such individual was of pure Bluewing appearance,
while another was Goldenwing, but with some trace of Bluewing coloration. I
do not know of anyone yet who has developed species-specific DNA markers to
analyze hybrids and to look at the correlation of song with genetics, with
the exception of mitochondrial DNA differences, noted below. But given the
strong component of learning in the development of song in passerines, there
is little doubt that in such closely related species as these warblers, each
can learn to sing an accurate rendition of the other's song. Such is the
case in Black-capped and Carolina chickadees, where such molecular markers
are being used to look at hybridization in their case. I have heard many
bilingual chickadees at their contact zone here in Virginia, and no doubt
many of these birds were hybrids. But that is more because birds at the
range interface, who are often likely to be hybrids, are also in a position
literally to hear the songs of both species as it is developing its own
song. Many hybrid chickadees, however, sing (at least predominantly) the
song of only one species (Carolina in the case of the Shenandoah Valley, for
instance). Within 2-4 miles perhaps of the chickadee range interface, many
birds are hybrids, but are going to be singing the song of the species
expected on that side of the hybrid zone. Song isn't a reliable marker of
the birds' genetics that close to the hybrid zone because of the opportunity
for "mislearning".
Also, Frank Gill did some DNA work on the warblers a while back, and showed
that in Golden-winged Warbler populations in the vicinity of Blue-winged
Warblers, many individuals can have mitochondrial DNA of Bluewings, even
though the Goldenwings look "pure". So the "Goldenwings" were technically
hybrids, as revealed by the mitochondrial DNA marker, even though they
looked and sounded pure.
Gene Sattler
Lynchburg, VA
-----Original Message-----
From: Spahr MD, John [mailto:Jspahr@xxxxxxxxxxxxxx]
Sent: Tuesday, May 21, 2002 10:03 AM
To: VA BIRD (E-mail)
Cc: Yulee Larner (E-mail); Steve Rannels (E-mail)
Subject: [va-bird] "Funny" Golden-winged Warbler -- Bath County
The Rockingham Bird Club had a wonderful birding retreat at Fort Lewis Lodge
in Bath County this past weekend. Over 90 species were encountered. Polly
Scott reported seeing a Golden-winged Warbler along Rt. 678 by the Riverside
House. Later when the group stopped at this site we heard the classic
distant "beeezz-buzzz" of a Blue-winged Warbler, but no one could see the
bird. No Golden-winged Warbler song was appreciated. Later that day as we
were heading home I spent some time searching for the bird and found it. By
plumage it was prototypical Golden-winged Warbler (no hybrid features). The
curious thing is that when watching the bird on a high perch one could see
it tilt its head back, open its beak and utter a classic *Blue-winged*
Warbler "beeezz-buzzz." I would wager a pair top dollar binoculars that any
hot-shot birder out there upon hearing that song would not instantly and
confidently consider it a Blue-winged song.
What is especially strange is that this is the SECOND such bird that I have
encountered. The other is a well known bird in Sussex County, NJ that was
seen and heard by countless top birders during the World Series of Birding,
for two years in a row now -- most viewed it and counted it as a
Golden-winged. That bird was actually digitally recorded by Steve Rannels
who plans to compare the sonogram with a known Blue-winged. We all know
these two species interbreed and one could expect hybrids to give either
call. But a typical Golden-winged singing a typical Blue-winged song is
unusual, I would think. Any one else ever encounter this?
John
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